South Korean biopharmaceutical company Celltrion has won an appeal case and successfully challenged the domestic patent of an original drug by Samsung Biogen, thereby clearing the way for sales of its up-and-coming biosimilar to treat autoimmune disorders, officials said Friday.

The Patent Court of Korea on Thursday upheld a judgment by the Intellectual Property Tribunal, invalidating Samsung Biogen’s patent on Rituxan, an original drug used to treat chronic lymphocytic leukemia.

The court decision effectively removed the last market hurdle for Truxima, Celltrion’s Rituxan-referencing biosimilar, which has been expanding its reach in overseas markets, officials said.

Truxima (Celltrion)

The biosimilar obtained the approval of the US Food and Drug Administration in November and recorded a 35 percent market share in Europe in the third quarter, marking the steepest growth among Celltrion’s main products.

In 2015, Celltrion had filed five separate lawsuits seeking the invalidation of Samsung Biogen’s patents for Rituxan. Of those cases, four had already resulted in judgments in Celltrion’s favor in 2016 and 2017. The latest case represented the final obstacle.

Under the current law biosimilar makers cannot launch their products, even after obtaining permission from health authorities, unless the patents for the original drugs are declared invalid.